Cleaning Transformer Insulation: Corrosive Sulfur Removal

Insulation of transformers must be reliably protected from harmful influences. One of the most aggressive impurities is corrosive sulfur, accumulated in the process of oil and winding insulation aging.

Types of transformer insulation

Transformer insulation system is divided into internal and external. The external insulation is the air between transformer bushings and the tank, as well as the winding bushings.

The internal insulation consists of winding insulation and is divided into main insulation and longitudinal insulation. There is liquid and solid insulation, or a combination. Solid and liquid insulation may suffer from the effects of corrosive sulfur. Apart from sulfur, solid dielectrics are subject to various physical and thermal factors.

The problem with overloads and internal insulation aging is that the cellulose is damaged irreversibly. High quality and good condition of insulation reduces the risks and extends transformer lifetime.

What makes corrosive sulfur dangerous to the insulation and the transformer

Timely detection of corrosive sulfur in transformer oil is important, because most dielectric oils are made from sour crude. As a rule, darkening of a copper strip in hot transformer oil is used as an indication of corrosive sulfur presence.

Oxidation of oil results in formation of various oxygen compounds, only some of which can be detected by the regulated oil testing methods. Besides, non-corrosive sulfur may become corrosive under certain operating conditions.

Corrosive sulfur is a serious threat to transformer reliability. Some of the problems caused by such sulfur are:

– catalysis of transformer oil aging with formation of colloids;

– accelerated formation of film on switch contacts and their overheating;

– negative impact on rubber seals;

– formation of conductive compounds of copper and sulfur on the windings and the consequent insulation damage.

The aging of transformer insulation due to corrosion causes the loss of dielectric properties of the oil among other problems. Corrosion destroys the metal in the transformer and causes equipment failure.

To prevent or solve the corrosion problem, cleaning of the insulation to corrosive sulfur removal is very important.

The GlobeCore transformer oil desulfurization process

There are several ways of desulfurization of oil:

  1. Chemical additives, such as boron fluoride, triflouroacetic acid, etc.
  2. Catalytic hydrotreatment.
  3. Adsorption.

All processes have both benefits and limitations. For instance, using an incorrect sorbent can not only fail to achieve the desired result, but actually harm the oil. Also, with even the smallest deviation from the process temperature, the properties of the insulation fluid may be lost, while the degradation process may be accelerated.

GlobeCore developed unique equipment to restore transformer oil properties, including desulfurization. This process is combined with the regeneration process, and results in transformer oil fully suitable for use.

Since each sorbent is only capable to remove a certain range of sulfur compounds, GlobeCore uses an optimal combination of various sorbents. The mixture is loaded into special columns; transformer oil then passes through the columns. The sorbent media remove both oil aging products and corrosive sulfur compounds.

GlobeCore oil purification equipment can be selected for very different specific client requirements and operating conditions. A wide range of both stationary and mobile units is available, with various processing capacities to suit the actual customer oil treatment needs.